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|United States Patent
May 21, 1996
Vessel inspection plug and method of installing same in vessel
An inspection plug assembly includes an elastomeric outer sleeve which may
be compressed into the skin of an insulating jacket for forming a seal
between the assembly and the jacket by mechanically anchoring the assembly
to the jacket, without requiring the use of adhesives. The plug includes
pull tabs to facilitate removal of the plug from the sleeves. A lanyard
may be attached to the plug and the jacket without disturbing the sealing
Webster; James (Spring, TX)
Sepco Industries (Houston, TX)
September 19, 1994
|Current U.S. Class:
|138/90; 138/89; 138/92
|Field of Search:
U.S. Patent Documents
|Greenwalt et al.
Primary Examiner: Bryant, III; James E.
Attorney, Agent or Firm: Curfiss; Robert C.
Butler & Binion
What is claimed is:
1. A resealable sealing assembly located in a cylindrically shaped
inspection hole cut in skin-covered insulation, the assembly comprising:
a. a cylindrically shaped plug made of an elastomeric material;
b. a rigid, formable, cylindrically shaped, hollow inner sleeve adapted for
receiving the plug; and
c. a compressible outer sleeve adapted to receive the inner sleeve, said
outer sleeve made of an elastomeric material, the inner and outer sleeves
being positioned in the inspection hole and secured therein by expanding a
portion of the inner sleeve and compressing the outer sleeve between the
inner sleeve and the skin-covered insulation.
2. The assembly of claim 1, the inner sleeve further including an annular
lip extending outwardly at the sleeve top and the outer sleeve having an
upper end adapted to be received within the annular lip.
3. The assembly of claim 2, the inner sleeve further including a peripheral
rim positioned outside the inner sleeve annular lip when the upper end of
the outer sleeve is in the annular lip.
4. The assembly of claim 1, the plug further including a pull tab extending
outwardly from the plug for facilitating removal of the plug from the
5. The assembly of claim 4, further including a lanyard attached to the
pull tab and having a free end adapted to be secured to the skin-covered
6. The assembly of claim 3, an enlarged bulge being formed in the inner
sleeve for clamping the insulation skin between the inner sleeve annular
lip and the bulge with the outer sleeve compressed into the skin to form a
water tight seal.
7. The assembly of claim 6, the plug further including a peripheral cleat
adapted to be received in and compressed into the bulge of the inner
8. The assembly of claim 7, the plug further including an annular lip
having a channel adapted for receiving the annular lip of the inner
sleeve, such that the plug annular lip is stretched and firmly held
against the outer sleeve when the cleat is compressed into the bulge.
9. A method for anchoring an inspection plug assembly of the type having a
sleeve and a plug in an inspection hole of the skin of a skin covered
insulation, comprising the steps of:
a. cutting a suitable inspection hole in the skin;
b. placing an elastomeric, deformable sleeve over an inspection plug
c. inserting the assembled sleeves in the hole; and
d. forming a bulge in the inspection plug at the site, for mechanically
anchoring the sleeve in the hole, and for compressing the elastomeric,
deformable sleeve into the skin for forming a seal therebetween.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The subject invention is generally related to resealable sealing assemblies
and is specifically directed to an improved vessel inspection plug and
assembly including an elastomeric plug and a receptive sleeve.
2. Discussion of the Prior Art
Many types of vessels and storage containers require periodic inspection
for early detection of corrosion, deterioration of wall thickness and the
like. In many typical installations, the vessels are insulated, making
visual inspection of the outer surface difficult and impractical without
disturbing the insulation. Typically, inspection holes are cut into the
insulation to permit inspection. The holes then must be closed and
resealed upon completion of inspection. Over the years, resealable sealing
assemblies have been developed that permit permanent inspection holes to
be cut into the insulation layer, with the assemblies being removable for
inspection and resealable upon completion.
An example of a resealable sealing assembly is disclosed in U.S. Pat. No.
4,091,842, entitled: "Resealable Sealing Assembly for Inspection Port
Hole", issued to E. L. Greenawalt, et al on May 10, 1978. As there
disclosed, the sealing assembly includes a rigid sleeve which is
permanently installed in the insulation port hole and a removable plug
made of a compressible elastomeric material which, when inserted in the
rigid sleeve, forms a weatherproof seal. This assembly has gained
widespread acceptance throughout the industry and is applicable in a wide
variety of textures of insulation from very soft and flimsy to hard. A
weatherproof, adhesive-sealant is used to bond the sleeve to the
insulation. An annular bulge is created in the sleeve to further
mechanically bond the sleeve to the insulation.
While the resealable sealing assembly of the prior art has been widely
accepted, it is not readily useful in applications where the insulation
layer is of a ribbed or corrugated configuration. In addition, removal of
the plug from the sleeve is somewhat cumbersome, particularly due to the
excellent sealing characteristics of the assembly.
Other resealable assemblies are disclosed in U.S. Pat. No. 3,827,462,
entitled: "Insulating Plug", issued to J. J. Celesta on Aug. 6, 1974; U.S.
Pat. No. 3,658,096, entitled: "Insulating Plug", issued to R. E. Higuera
on Apr. 25, 1972 and U.S. Pat. No. 3,233,775, entitled: "Flexible Plastic
Plug", issued to J. S. Bozek on Feb. 8, 1966. None of the disclosed
assemblies is readily adaptable for use with a ribbed or corrugated
Therefore, there is a need for an improved sealing assembly that is readily
adaptable to both smooth and ribbed insulation configurations and for an
improved plug which is easy to remove and replace in the assembly.
SUMMARY OF THE INVENTION
The subject invention is directed to an improved inspection plug assembly
including a sleeve adapter particularly well suited for corrugated or
ribbed insulation jacketing and a tabbed plug for ease of removal. The
plug is also permanently attached to the system assembly, minimizing risk
of misplacement during an inspection. It is an added advantage that the
assembly of the subject invention may be installed in a rigid wall system,
whether or not corrugated, without the use of the heretofore required
In the preferred embodiment of the invention, the inspection plug assembly
includes a rigid, initially cylindrical inner sleeve, a compressible plug
adapted to be snugly fit in the inner sleeve and an elastomeric outer
sleeve surrounding the outer circumferential surface of the inner sleeve.
In the preferred embodiment, the inner sleeve has a lip, against which the
elastomeric sleeve is seated. Preferably, the outer sleeve includes a
circumferential ridge adapted to seat firmly against the lip, with the
upper end of the sleeve received in the lip. It is desirable to provide
tabs on the plug to facilitate easy removal. In the preferred embodiment,
a tether may be attached to one of the tabs, with an opposite end attached
to the jacket for minimizing risk of misplacement of the plug during
The sealing assembly is mounted in the insulation jacket by cutting a
through hole in the insulation the nominal size of the outer sleeve when
the outer sleeve is positioned on the inner sleeve. The through hole
exposes the vessel wall for inspection. The assembled inner and outer
sleeve are then inserted in the hole, with a portion of the outer sleeve
above and a portion of the outer sleeve below the corrugated jacket or
skin of the insulation. In the preferred embodiment, the ridge on the
outer sleeve may be firmly seated against the corrugated jacket. A portion
of the inner sleeve, inside the jacket is then hydraulically expanded to
anchor the sleeves in the hole. The elastomeric outer sleeve bites into
the corrugated wall to provide a water-tight seal between the sleeves and
the jacket. Removed insulation may then be placed in the hole and covered
with the plug which is inserted in the sleeve. The plug may now be removed
as required in order to perform periodic inspections.
It is, therefore, an object and feature of the subject invention to provide
an improved inspection plug assembly which is ideally suited for use with
corrugated or ribbed insulation jackets.
It is another object and feature of the subject invention to provide an
inspection plug assembly wherein the water tight seal between the plug
assembly and the insulation jacket can be achieved without the use of
It is a further object and feature of the subject invention to provide for
an enhanced inspection plug with easy removal tabs and a lanyard system
for securing the plug to the final assembly.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an exploded perspective view of the inspection plug and sleeve
FIG. 2 illustrates the inner and outer sleeves assembled for insertion in
the hole of an insulating jacket.
FIG. 3 is a view showing the sleeves positioned in the hole of an
insulating jacket and ready to be anchored therein.
FIG. 4 shows the sleeves as finally assembled and anchored in the hole of
an insulating jacket, with the plug in the assembly and tethered to the
FIG. 5 is a view similar to FIG. 1, showing the assembled inspection plug
and sleeve assembly installed in the wall of a vessel.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The preferred embodiment of the subject invention includes the plug and
sleeve assembly as shown in FIG. 1. Specifically, the assembly includes a
rigid inner sleeve 10, made of a substantially rigid , ductile material
which is preferably cold-formable, such as, by way of example, aluminum,
an outer sleeve 14 and a plug 15. The sleeve 10 is essentially a hollow
cylinder which has an annular lip 12, formed at the outer end of the
sleeve. The outer lip is expanded sufficiently that it cannot pass through
the hole in the insulating jacket.
The outer sleeve 14 is also generally a hollow cylinder with an inside
diameter dimensioned to snugly fit over the outer wall of the inner sleeve
10. Typically, the outer sleeve is made of a compressible elastomeric
material having a durometer as measured on Shore "A" scale of from about
20 to 60, and more preferably having a durometer of from about 35 to 45.
Examples of suitable elastomeric materials are Silastic brand silicon
rubbers, flexible polyurethane, Viton brand, Neoprene brand and other
In the preferred embodiment, the upper end of the outer sleeve 14 includes
a radius 16 adapted to slide into the lip 12 of the inner sleeve. A
peripheral ridge 18 is positioned under the radius 16 and is adapted to be
seated adjacent the lower, outer edge 20 of the lip. This ridge assures
that the inner sleeve 14 does not slip through the hole in the insulation
jacket during the installation procedure.
The assembly is now ready to be installed in a suitable mounting hole 21
provided in the skin of a typical insulation jacket 22, as best shown in
FIG. 5. As shown in FIG. 3, the insulation jacket generally comprises a
rigid or semi-rigid outer skin for sheathing a layer of insulation 24. In
the illustrated embodiment, the skin 22 is ribbed or corrugated, but the
invention is equally suited for smooth rigid skin application. The nominal
size of the mounting hole 21 is slightly larger than outer peripheral
surface of the outer sleeve 14, permitting a contacting, sliding fit of
the outer sleeve, inner sleeve assembly of FIG. 2 into the hole 21.
Typically, the mounting hole 21 is cut at the installation site at the
time of installation, using a hole cutting tool or similar device. The
insulation behind the jacket 22 and within the hole is then removed. The
assembled inner and outer sleeves 10 and 14 are then inserted in the hole,
as shown in FIG. 3. After insertion of the sleeve assembly into the hole
21, an annular bulge 26 is formed in the rigid wall of inner sleeve 10, as
shown in FIG. 4. This also expands the elastomeric sleeve 14. This bulge
26 can be formed by any of several means. Preferably, the material from
which sleeve 10 is formed can be cold formed in place using a hand held
Using cold formable materials has the advantage of being able to use hand
tools and low temperatures in forming the annular bulge 26. Such an
advantage is particularly useful in the subject application, and provides
an added safety feature particularly where sparks or fires are not
desirable. Of course, where such issues do not create safety risks, heat
reactive materials such as thermoplastics may be substituted for cold
formable alloys and the like.
The bulge 26 firmly anchors the sleeve assembly in the jacket by clamping
it between the sleeve lip 12 and the bulge. The elastomeric outer sleeve
14 fills any gap between the inner sleeve 10 and the jacket 22 and is
deformed sufficiently to fill any voids and form a water tight seal
between the sleeve assembly and the insulating jacket. This configuration
and assembly eliminates the requirement for an adhesive bonding agent in
order to form a water tight seal between the sleeve and the jacket.
However, it will of course be understood that, an adhesive bond such as
that disclosed in the aforementioned U.S. Pat. No. 4,091,842 could be used
in combination with the assembly of the subject invention where a
secondary or back-up seal is desired.
Once the bulge 26 is formed, and the sleeve assembly is firmly anchored in
the hole 21 of the jacket 22, the insulation removed from the hole may be
replaced and the plug 15 may be inserted in the sleeve to close and seal
the hole. The plug 15 is an essentially hollow, one-piece cylinder having
a diaphragm 30, an annular lip 32 and an annular cleat 34. The plug 15 may
be molded into a single piece from an elastomeric material, such as
Silastic brand silicon rubber or the like. The outside diameter of the
plug wall 36 between lip 32 and cleat 34 is sufficiently small so as to
fit within the sleeve 10 once the sleeve is anchored in the hole 21 of the
insulating jacket 22. It is not essential that there be full contact
between the plug wall 36 and the sleeve 10, since this area is not relied
upon to provide the seal between the plug and the sleeve.
The diaphragm 30 prevents passage of air and/or moisture through the
interior of the plug 15. It can be located any where along the wall 36 of
the plug and, as here shown near the cleat 34, merely as a matter of
design choice, and to facilitate ease of insertion of the plug in and
removal of the plug from the sleeve 10. The annular lip 32 extends
outwardly from the top of the side wall 36 of the plug in a generally
radial direction. The size and shape of the lip is not critical, except
for the lower wall 38 which is concave formed to define a channel 39 which
is adapted to fit over and receive the annular lip 12 of the sleeve 10.
This forms one of the sealing surfaces between the plug and the sleeve
The annular cleat 34 protrudes generally radially outward from the wall 36
of the plug, and is preferably, although not necessarily, located near the
bottom of the plug wall. The specific shape of the cleat is not critical,
other than that it is adapted to be compressed into the channel in the
sleeve 10 which is formed by the bulge 26. Specifically, the bulge channel
provides a surface for receiving and compressing the cleat 34 when the
plug 15 is fully inserted in the sleeve with the plug lip 32 properly
seated and sealed against sleeve lip 12. The formation of the bulge/cleat
surface to surface seal is accomplished by having the interior diameter of
the sleeve bulge channel 26 sufficiently smaller than the outside diameter
of the plug cleat 34. Thus, when the elastomeric plug 15 is inserted and
seated in the rigid sleeve 10, the cleat 34 is compressed and deformed
within the bulge channel so that its surface tightly mates with the
interior surface of the sleeve.
The location of the cleat 34 relative to the top of the plug lip 32 is
slightly more than the distance between the plug cleat 34 and the top of
the curve of radius on the inner wall of the lip. This causes the plug
wall 36 to pull downwardly on the lip 32 when the cleat is inserted in the
bulge channel, stretching the plug lip 32 over the sleeve lip 12, thereby
forming a second surface to surface seal between the plug and the sleeve.
A very stable weather proof overall seal is formed between the plug 15 and
the sleeve 10 by use of the dual sealing system.
The preferred plug embodiment of the subject invention includes a pair of
extended tabs 40, 42 formed in and projecting outwardly from the plug lip
32. As best seen in FIG. 5, the tabs may be grasped between the fingers
and thumbs in order to facilitate removal of the plug from the sleeve.
Where desired, a through hole 44 may be provided in either or both of the
tabs, permitting a tether line or lanyard 46 to be attached to the plug
without disturbing the sealing integrity of the plug. The free end 48 of
the lanyard may be suitably secured to the jacket 21, minimizing risk of
misplacing the plug during an inspection operation.
While certain features and embodiments of the invention have been disclosed
in detail herein, it will be understood that the invention includes all
modifications and enhancements within the scope and spirit of the